Method of producing a fertilizer of urea



May 18 1926,

J, H. LIDHOLM METHOD OF PRODUCING "A FERTIIJI.ZER 0F UREA Filed Jan. 9. 1924 Patented May 18, 1926.

T-UNITED STATES 1,584,875 PATENT OFFICE.

1 mm HJALMAB LIDHOLM, or waneon, swnnnn.

METHOD OF PRODUCING A FERTILIZER 0F UREA.

; ga 'naaon filed: January 9, 1924. Serial No. seam.

The invention relates to an improved fertilizer and a process for making the same. It is well-known that urea has a high value as fertilizer inasmuch as it contains about 45% of nitrogen insuch state that it can be easily assimilated by plants. It can be produced technically on a large scale from calcium .cyanamide as a dilute aqgleeous solution from whichthe solid urea can obtained by concentratin the solution and then cooling it to crysta lize the urea. lhe urea produced in this manner is obtained as "long needle-like crystalsforming a felted mass which readily takes up moisture from the atmosphere so that the storing of such product is diflicult and its spreading on the field by means of the usual sowing and fertilizer spreading machines is impossible.

I have now found that a urea of quite difierent properties especially usefulas fertilizer is obtained by fusing urea containing a small content of water, and then solidifying it by cooling. Anhydrous urea has a melting point of 132 to 133 but the technically manufactured urea Whlch usually contains some water melts at a temperature of 80 to 90 C. dependent on its percentage of water. The'molten urea can be molded-into blocks which on sellgrains by suspending the molten mass as" drops in a gas 1n which the drops are cooled so that they become solid when falling through it. In the latter case the urea is obtained as grains having a more or less regular rounded form, i. e. as spheroids and shows-no tendency to cake together in storin so that it' can easily be spread on the field by means of the usual machines. Also by crushing the solid blocks of urea manufactured b casting molten urea a granular or pulverulhnt product is obtained which on storing remains dry and, therefore, is suitable to use as fertilizer.

Accordin to the invention the-urea so1utio'n'is pre erably evaporated until its content oi water does not exceed 10%, which may be donewithout the deposition of solid c0; urea." Upon cooling the liquid produced by such evaporation, it solidifies completely.

In the accompanying shown diagrammatically one embodiment of an apparatus for 'carryin out the process of the invention. Fig. 1 s ows a side view of the apparatus partly in section and Fig. 2

are crushed, or the.

drawing I have shows a cross-sectional view of the nozzle on the line 22 of Fig. 1-.

Referring to the drawing, 1 is an evapcrating pan of any well-known construction in'which an aqueous solution of urea can be evaporated in bulk to such concentration that its content on water will be reduced to about 10 to 3%. At said percentage of water urea melts at a temperature of about to 9Q C. and during the evaporation the temperature in the pan is held somewhat above said value. The molten urea is drawn ofi through a pipe 2 having a nozzle 3 consisting of a plate which has a passage 4 ending with an upwardly directed mouth. Above the nozzle 3 a chamber for pressure air is provided the air being supon the pressure used, and the drops ing a more or less regular rounded form.

The invention is, of course, not limited to the use of the device shown in the drawing for the manufacture of the product asany well-known means for dividing a. liquid into drops may be used, such asnozzles of different kinds, rotating discs, and so on. dividing into dropsof the molten urea can take place in the .open air or in a closed chamber to which air or other gas is supplied as cooling medium. 1

WVhat'I claim is p I 1. The process of preparing urea for'nse' as a ferti izer which comprises evaporating The a solution of urea in-bulk to produce a liquid 7 evaporation.

2. Theprocess of preparing urea for use as a fertilizer which comprises evaporating a solution of urea in bulk to produce aliquid containing not more than about 10 percent of water, and then suspending the liquid as drops ina gas of such temperature that the drops solidify snbstantiall without further evaporation to produce sp eroidal granules.

3. A new product comprising non-hygroscopic solid urea of dense internal structure, such as can be produced by the herein described process of cooling to solidification wifihout subs santial evaporation a liquid containing urea and not more than 10 percent of water.

4. A. new product comprising non-by scopic solid urea in the form of sphero d l granules of dense internal structure, such as can be produced by the hereindescribed process of cooling to solidification without substantial evaporation gas-suspended drops of 1 In testimony whereof I have signed my name.

JOHAN HJALMAR LIDHOLM. 

